DC Fast-Charging Cooling Control for Condensation-Safe Battery Charging
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Solution Overview
Problem
Existing electric vehicle battery systems face challenges in meeting DCFC requirements due to excessive thermal derating, which can lead to condensation and isolation failures under high humidity conditions, and energy gain is negatively impacted by maintaining a constant coolant temperature during charging.
Innovation Solution
A smart cooling strategy that varies coolant temperature based on rechargeable energy storage system conditions and environmental factors, adjusting the temperature setpoints dynamically to optimize DCFC performance and minimize condensation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lower coolant temperature is used during DCFC charging, then higher currents can be enabled without exceeding thermal limits, but condensation and isolation failures occur under high humidity conditions
Solution Approach 1:
The coolant temperature is changed from a static constant value to a dynamic variable that adjusts based on real-time conditions. The control system continuously monitors ambient temperature, RESS cell temperature, voltage, SOC, and charging current to dynamically set the coolant temperature, enabling the system to adapt between preventing condensation and managing thermal limits
Solution Approach 2:
The coolant temperature setpoint is adjusted as a variable parameter rather than a fixed value. The system implements multiple temperature setpoints (e.g., 20°C, 15°C, 25°C or 30°C) that are selected based on operating conditions, allowing optimization of charging current while preventing condensation-related isolation failures
2Reliability
If a constant coolant temperature of 20°C is maintained during DCFC, then condensation risks are reduced, but energy gain is negatively impacted due to excessive thermal derating
Solution Approach 1:
The coolant temperature transitions from a constant 20°C setting to a dynamic control strategy that adjusts temperature based on ambient conditions, RESS cell temperature, voltage, SOC, and charging current. This enables the system to raise coolant temperature when conditions allow, improving energy gain while maintaining condensation prevention when needed
Solution Approach 2:
The system implements variable coolant temperature setpoints (e.g., 20°C, 15°C, 25°C or 30°C) that are selected based on real-time operating parameters. By changing the temperature parameter dynamically, the system optimizes the balance between preventing condensation and maximizing energy gain during DCFC charging
3Temperature
If the battery pack is cooled down too much during DCFC, then thermal limits are maintained, but energy gain is negatively impacted
Solution Approach 1:
The coolant temperature control is dynamically adjusted based on the difference between RESS cell temperature and thermal limits. The system monitors voltage, SOC, and charging current to determine appropriate cooling levels, allowing the battery to operate closer to thermal limits when conditions permit, thereby improving energy gain while maintaining safety
Solution Approach 2:
The system implements variable coolant temperature setpoints that adjust based on thermal conditions and charging parameters. By changing the temperature parameter from a fixed low value to a dynamic setpoint that can be higher when conditions allow, the system optimizes energy gain while maintaining thermal limit control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The strategy enhances DCFC performance by enabling higher currents without exceeding thermal limits, reducing condensation risks, and optimizing energy gain by adjusting coolant temperature based on RESS conditions and ambient air temperature.
Implementation Method 1
utilizing a lower CT (coolant temperature) from the beginning of the DCFC charge process
Implementation Method 2
coolant temperature (CT) based on RESS conditions and surrounding environment conditions
Implementation Method 3
utilizing a lower CT from the beginning of the DCFC charge process may introduce condensation and corresponding loss of isolation failures in the RESS under high humidity operating conditions
Data Source
AI summary
A method, system, and motor vehicle for controlling a direct-current fast-charging process of a battery system are provided that significantly improves performance of the direct-current fast-charging process and minimizes condensation issues by utilizing lower coolant temperature for a short duration when a rechargeable energy storage system cell temperature is greater than a specific temperature threshold. The rechargeable energy storage system cell temperature, a rechargeable energy storage system state of charge a rechargeable energy storage system voltage, and a rechargeable energy storage system direct-current fast-charging current are utilized to determine when to utilize the lower coolant temperature when the rechargeable energy storage system cell temperature is greater than a specific temperature threshold instead of using a lower coolant temperature from the beginning of the direct-current fast-charging process.